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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Bruijnzeels 3 Internet-Draft NLnet Labs 4 Intended status: Standards Track C. Martinez 5 Expires: April 19, 2019 LACNIC 6 R. Austein 7 Dragon Research Labs 8 October 16, 2018 10 RPKI Signed Object for Trust Anchor Keys 11 draft-ietf-sidrops-signed-tal-02 13 Abstract 15 Trust Anchor Locators (TALs) [I-D.ietf-sidrops-https-tal] are used by 16 Relying Parties in the RPKI to locate and validate Trust Anchor 17 certificates used in RPKI validation. This document defines an RPKI 18 signed object for Trust Anchor Keys (TAK), that can be used by Trust 19 Anchors to signal their set of current keys and the location(s) of 20 the accompanying CA certiifcates to Relying Parties, as well as 21 changes to this set in the form of revoked keys and new keys, in 22 order to support both planned and unplanned key rolls without 23 impacting RPKI validation. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on April 19, 2019. 42 Copyright Notice 44 Copyright (c) 2018 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 60 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. TAK Object definition . . . . . . . . . . . . . . . . . . . . 4 62 3.1. The TAK Object Content Type . . . . . . . . . . . . . . . 5 63 3.2. The TAK Object eContent . . . . . . . . . . . . . . . . . 5 64 3.2.1. version . . . . . . . . . . . . . . . . . . . . . . . 5 65 3.2.2. current . . . . . . . . . . . . . . . . . . . . . . . 5 66 3.2.3. revoked . . . . . . . . . . . . . . . . . . . . . . . 6 67 3.3. TAK Object Validation . . . . . . . . . . . . . . . . . . 6 68 4. Maintaining multiple TA keys . . . . . . . . . . . . . . . . 7 69 4.1. Prepare a new TA key . . . . . . . . . . . . . . . . . . 7 70 4.2. Publishing for Multiple TA Keys . . . . . . . . . . . . . 7 71 5. TAK Object Generation and Publication . . . . . . . . . . . . 8 72 6. Performing TA Key Rolls . . . . . . . . . . . . . . . . . . . 9 73 6.1. Opting in to Key Rolls . . . . . . . . . . . . . . . . . 10 74 6.1.1. Trust Anchor . . . . . . . . . . . . . . . . . . . . 10 75 6.1.2. Relying Parties . . . . . . . . . . . . . . . . . . . 12 76 6.2. Pre-stage a New Key . . . . . . . . . . . . . . . . . . . 12 77 6.2.1. Trust Anchor . . . . . . . . . . . . . . . . . . . . 12 78 6.2.2. Relying Parties . . . . . . . . . . . . . . . . . . . 14 79 6.3. Planned Key Revocation . . . . . . . . . . . . . . . . . 14 80 6.3.1. Trust Anchor . . . . . . . . . . . . . . . . . . . . 14 81 6.3.2. Relying Parties . . . . . . . . . . . . . . . . . . . 17 82 6.4. Unplanned revocation . . . . . . . . . . . . . . . . . . 17 83 6.4.1. Trust Anchor . . . . . . . . . . . . . . . . . . . . 17 84 7. Deployment Considerations . . . . . . . . . . . . . . . . . . 18 85 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 86 8.1. OID . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 87 8.2. File Extension . . . . . . . . . . . . . . . . . . . . . 19 88 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 89 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 90 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 91 11.1. Normative References . . . . . . . . . . . . . . . . . . 19 92 11.2. Informative References . . . . . . . . . . . . . . . . . 21 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 95 1. Requirements notation 97 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 98 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 99 "OPTIONAL" in this document are to be interpreted as described in BCP 100 14 [RFC2119] [RFC8174] when, and only when, they appear in all 101 capitals, as shown here. 103 2. Overview 105 Trust Anchor Locators (TALs) [I-D.ietf-sidrops-https-tal] are used by 106 Relying Parties in the RPKI to locate and validate Trust Anchor (TA) 107 certificates used in RPKI validation. However, until now there has 108 been no formal way of notifying Relying Parties (RP) of updates to a 109 TAL. Such updates may be needed in particular in case a Trust Anchor 110 needs to perform a planned, or unplanned, key roll. 112 This document defines a new RPKI signed object that can be used to 113 document the current set of keys and the loctaion(s) of the 114 accompanying CA certificates, as well as any changes to this set. 115 This allows RPs to be notified automatically of such changes, and 116 enables Trust Anchors to pre-stage a number of operational keys so 117 that planned and unplanned key rolls can be performed without risking 118 the invalidation of the RPKI tree under the TA. We call this object 119 the Trust Anchor Keys (TAK) object. 121 When Relying Parties (RPs) are first bootstrapped, they use any 122 current TAL to discover a key and location(s) of the TA 123 certificate(s) for a TA. The RP can then retreive and validating the 124 TA certificate, and subsequently validate the manifest [RFC6486] and 125 CRL [section 5 of @!RFC6487]. However, before processing any other 126 objects it will then first validate the TAK object, if present. All 127 enumarated new keys (and locations) are then added to a new list of 128 current TA keys for this TA. The RP will then recursively fetch and 129 validate the TA certificates, manifest, CRL and TAK objects for each 130 of these keys. As a part of this process the RP will also compile a 131 list of revoked keys enumarated by any of the validly signed TAK 132 objects. As the final step the RP will then filter out any revoked 133 TA keys from its new set. This new set now replaces the previous 134 set. 136 If the key used to start this process is still considered current, 137 then validation continues. But if the key was revoked, then 138 validation is restarted using one of the remaining keys in the set. 140 This process allows Trust Anchors to operate a set of N current keys, 141 where any key can effectively revoke any or all of the other keys to 142 perform either a planned, or an unplanned, key roll. This also 143 allows Trust Anchors to produce long lived TAK objects as forward 144 pointers to RPs, and retire its old key when doing a key roll. 146 While the generic process is quite involved, the amount of work 147 needed to support an envisioned normal key roll is fairly limited. 148 Under normal circumstances a TA will typically have two current keys, 149 so that is can perform an emergency roll over in case one of the keys 150 is lost. This means that the RP will need to validate two TAK 151 objects. However, typically these files will agree that both keys 152 are current and validation continues. 154 When a key roll is executed a TA will remove one old key, and 155 introduce one new (back-up) key. The RP will remove the old key from 156 its set, and it will not be queried again, and it will add the new 157 key and its TA certifcate location(s). 159 Only in a situation where an RP is very outdated can it be expected 160 that the RP will have to discover several chained TAK object. But, 161 since it will remove the outdated TALs in this process, this presents 162 a one time cost only. 164 Note that in theory a TA can revoke all of its keys and make itself 165 obsolete. In practice however, a well operated TA will have measures 166 in place to prevent this. Furthermore they can protect themselves 167 against key loss to adversaries through the use of such as the use of 168 a Hardware Security Module (HSM) to protect keys. Protecting against 169 this mis-operation would incur complexity and guesswork on the RPs. 170 Therefore it is believed that it is best to keep the process 171 straightforward, and offer a solution for the more likely issues of 172 loss of a key, e.g. because an HSM or card set is broken, and 173 planned key rolls. 175 3. TAK Object definition 177 The TAK object makes use of the template for RPKI digitally signed 178 objects [RFC6488], which defines a Crytopgraphic Message Syntax (CMS) 179 [RFC5652] wrapper for the Signed TALs content as well as a generic 180 validation procedure for RPKI signed objects. Therefore, to complete 181 the specification of the TAK object (see Section 4 of [RFC6488]), 182 this document defines: 184 o The OID defined in Section 3.1 that identifies the signed object 185 as being a TAK. (This OID appears within the eContentType in the 186 encapContentInfo object as well as the content-type signed 187 attribute in the signerInfo object). 189 o The ASN.1 syntax for the TAK eContent defined in Section 3.2. 191 o Additional steps to the validation steps specified in [RFC6488] 192 required to validate the TAK, defined in Section 3.3. 194 3.1. The TAK Object Content Type 196 This document requests an OID for TAK objects as follows: 198 signed-Tal OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) 199 rsadsi(113549) pkcs(1) pkcs9(9) 16 id-smime (1) TBD } 201 This OID MUST appear both within the eContentType in the 202 encapContentInfo object as well as the content-type signed attribute 203 in the signerInfo object (see [RFC6488]) 205 3.2. The TAK Object eContent 207 The content of a TAK object is ASN.1 encoded using the Distinguished 208 Encoding Rules (DER) [X.690], and is defined as follows: 210 TAK ::= SEQUENCE { 211 version INTEGER DEFAULT 0, 212 current ::= SEQUENCE SIZE (1..MAX) OF CurrentKey, 213 revoked ::= SEQUENCE OF SubjectPublicKeyInfo 214 } 216 CurrentKey ::= SEQUENCE { 217 certificateURIs SEQUENCE SIZE (1..MAX) OF CertificateURI, 218 subjectPublicKeyInfo SubjectPublicKeyInfo 219 } 221 CertificateURI ::= IA5String 223 SubjectPublicKeyInfo ::= SEQUENCE { 224 algorithm AlgorithmIdentifier, 225 subjectPublicKey BIT STRING 226 } 228 3.2.1. version 230 The version number of the TAK object MUST be 0. 232 3.2.2. current 234 This field defines the set of current keys (CurrentKey) according to 235 the signer of this Signed TALs object. 237 3.2.2.1. CurrentKey 239 This field defines a current TA Key, equivalent to [I-D.ietf-sidrops- 240 https-tal]. This structure contains a sequence of one or more URIs 241 and a SubjectPublicKeyInfo. 243 3.2.2.1.1. certificateURIs 245 This field is equivalent to the URI section in section 2.1 of 246 [I-D.ietf-sidrops-https-tal]. It MUST contain at least one 247 CertificateURI element. Each CertificateURI element contains the 248 IA5String representation of either an rsync URI [RFC5781], or an 249 HTTPS URI [RFC7230]. 251 3.2.2.1.2. subjectPublicKeyInfo 253 This field contains a SubjectPublicKeyInfo [section 4.1.2.7 or 254 @!RFC5280] in DER format [X.690]. 256 3.2.3. revoked 258 This field contains the list of keys, identified by 259 SubjectPublicKeyInfo, that are no longer to be used according to the 260 signer of this document. 262 3.3. TAK Object Validation 264 To determine whether a TAK object is valid, the RP MUST perform the 265 following steps in addition to those specified in [RFC6488]: 267 o The eContentType OID matches the OID described in Section 3.1 269 o The TAK object appears as the product of a Trust Anchor CA 270 certificate. 272 o This Trust Anchor CA has published only one TAK object in its 273 repository for this key, and this object appears on the Manifest 274 as the only entry using the ".tak" extension (see [RFC6481]). In 275 case more than one TAK object is found, all such objects MUST be 276 considered invalid. 278 o The EE certificate of this TAK object describes its Internet 279 Number Resources (INRs) using the "inherit" attribute 281 o The decoded TAK content conforms to the format defined in 282 Section 3.2. 284 If the above procedure indicates that the manifest is invalid, then 285 the TAK object MUST be discarded and treated as though no TAK object 286 were present. 288 4. Maintaining multiple TA keys 290 As described in Section 6 a TA will most likely choose to operate two 291 keys at any one time in order to be prepared for an emergency key 292 roll. When a TA operates multiple keys, each key MUST use its own CA 293 repository publication point as described in [RFC6481]. The CRL and 294 Manifest [RFC6486] for each of these keys will be unique to each key, 295 but the TA MUST ensure that equivalent CA certificates and RPKI 296 signed objects are issued under each key. Note that this is similar 297 to how such certificates and RPKI signed objects are re-issued as 298 part of a lower level CA key roll, described in section 4 of 299 [RFC6489]. 301 4.1. Prepare a new TA key 303 The Trust Anchors MUST generate a new key pair and generate a new TA 304 Certificate. For the Subject Information Access (see section 4.8.8.1 305 of [RFC6487]) this MUST use URIs that will be used by the new key to 306 publish objects. These URIs MUST be uniqe for use by this new key 307 only. The Internet Number Resources on this new certificate MUST be 308 equivalent to those found on the current certificate. 310 The new TA certificate MUST be published under one or more new 311 Certificate URIs for use by this new key only. 313 As decribed above, the TA MUST issue and publish equivalent CA 314 certificates and RPKI signed objects under this new key. 316 It is RECOMMENDED that the TA now generates a new TAL 317 [I-D.ietf-sidrops-https-tal] and verifies that the new Trust Anchor 318 certificate can be retrieved from all locations, and that it 319 generates the same results when it is used for top-down validation 320 instead of (any of) the current TA key(s). 322 Note that the TA MAY choose to make this TAL available to Relying 323 Parties, in particular to those that do not support TAK objects, and 324 for inclusion in the distribution of RP software in order to minimise 325 the overhead in bootstrapping fresh installations. 327 4.2. Publishing for Multiple TA Keys 329 If a TA uses a single remote publication server for its keys using 330 the RPKI publication protocol [RFC8181], then it MUST include all 331 and PDUs for the products of each of its keys 332 in a single query in order to ensure that they will reflect the same 333 content at all times. 335 If a TA uses multiple publication servers then it is by definition 336 inevitable that the content of different keys will be out of sync at 337 times. In such cases the TA SHOULD ensure that the duration of these 338 moments are limited to the shortest possible time. Furthermore the 339 following should be observed: 341 o It is strongly RECOMMENDED that TAs do not issue any RPKI Signed 342 Objects, such as ROAs [RFC6482], but limit their operations to 343 maintaining a CRL, Manifest and CA certificates only. If an 344 organisation maintaining a TA has an operational need for such 345 objects then it is strongly RECOMMENDED that they operate a 346 separate non-TA CA as a child of their TA for these operations. 347 If this approach is used the remaining issues regarding temporary 348 inconsistencies between multiple TA key repository publication 349 points is greatly reduced. 351 o In cases where a CA certificate is revoked completely, or replaced 352 by a certifcate with a reduced set of resources, these changes 353 will not take effect fully until all the TA keys repository 354 publication points have been updated. Given that TA key 355 operations are normally performed infrequently we don't expect 356 that this is a problem. I.e. if the revocation or shrinking of an 357 issued CA certificate is staged for days, or weeks anyway, then 358 experiencing a delay of several minutes for the repository 359 publication points to all be updated is fairly insignificant. 361 o In cases where a CA certificate is replaced by a certifcate with 362 an extend set of resources the TA MUST inform the receiving CA 363 only after all its repository publication points have been 364 updated. This ensures that the receiveing CA will not issue any 365 products that could be invalid if an RP uses a TA key just before 366 the CA certificate was due to be updated. 368 5. TAK Object Generation and Publication 370 A TA MAY choose to use TAK objects to communicate its set of current, 371 and revoked keys. If a TA chooses to use TAK objects, then it SHOULD 372 generate and publish TAK objects under each of its current keys. An 373 exception to this rule exists when a TA has lost permanent access to 374 one of its keys or the accompanying repository publication point. In 375 such cases however, the key in question MUST be revoked as described 376 below in Section 6. 378 A non-normative guideline for naming this object is that the filename 379 chosen for the Signed TAL Object in the publication repository be a 380 value derived from the public key part of the entity's key pair, 381 using the algorithm described for CRLs in section 2.2 of [RFC6481] 382 for generation of filenames. The filename extension of ".tak" MUST 383 be used to denote the object as a TAK. Note that this is in-line 384 with filename extensions defined in section 7.2 of [RFC6481] 386 In order to generate the TAK Objects, the TA MUST perform the 387 following actions: 389 o The TA MUST generate a key pair for a "one-time-use" EE 390 certificate to use for the TAK 392 o The TA MUST generate a one-time-use EE certificate for the TAK 394 o This EE certificate MUST have an SIA extension access description 395 field with an accessMethod OID value of id-ad-signedobject, where 396 the associated accessLocation references the publication point of 397 the TAK as an object URL. 399 o As described in [RFC6487], an [RFC3779] extension is required in 400 the EE certificate used for this object. However, because the 401 resource set is irrelevant to this object type, this certificate 402 MUST describe its Internet Number Resources (INRs) using the 403 "inherit" attribute, rather than explicit description of a 404 resource set. 406 o This EE certificate MUST have a "notBefore" time that matches, or 407 predates the moment that the TAK will be published. 409 o This EE certificate MUST have a "notAfter" time that reflects the 410 intended duration for which this TAK will be published. If the EE 411 certificate for a Signed TAL is expired, it MUST no longer be 412 published, but it MAY be replaced by a newly generated TAK object 413 with equivalent content and an updated "notAfter" time. 415 o The same set of current keys (see Section 3.2.2) MUST be included 416 on each TAK object for each current key. 418 o The TAK object MUST include all revoked keys (see Section 3.2.3) 419 that became revoked while the key signing the TAK in question was 420 current. 422 6. Performing TA Key Rolls 423 6.1. Opting in to Key Rolls 425 6.1.1. Trust Anchor 427 For simplicitly let's start with a situation where a TA has only one 428 key. The TA wants to start using TAK objects to perform key rolls in 429 future, so it introduces a TAK object under its single key 'A'. The 430 repository structure looks as follows (irrelevant details omitted): 432 +--------------------+ 433 | A.MFT | 434 +--------------------+ 435 | A.CRL | 436 | A.TAK | 437 | C1-A.CER | 438 | C2-A.CER | 439 +--------------------+ 441 +--------------------+ 442 | A.CRL | 443 +--------------------+ 444 | revocations.. | 445 +--------------------+ 447 +--------------------+ 448 | A.TAK | 449 +--------------------+ 450 | current: A | 451 | revoked: none | 452 +--------------------+ 454 +--------------------+ 455 | C1-A.CER | 456 +--------------------+ 457 | resources: C1 res | 458 | subject: C1 name | 459 | pub key: C1 key | 460 | SIA: C1 SIAs | 461 | AKI: A | 462 +--------------------+ 464 +--------------------+ 465 | C2-A.CER | 466 +--------------------+ 467 | resources: C2 res | 468 | subject: C2 name | 469 | pub key: C2 key | 470 | SIA: C2 SIAs | 471 | AKI: A | 472 +--------------------+ 474 So, the TA publishes a CRL and MFT under its key A, listing a TAK 475 object and in this case two certificates issued to children 'C1' and 476 'C2' signed using key A. The TAK object lists key 'A' as the only 477 current key, and has no revoked keys. 479 6.1.2. Relying Parties 481 Relying Parties who have a TAL for key 'A' configured will discover 482 the TAK object. If the RP does not support this object, it will 483 reject this object but continue to validate the remaining RPKI tree 484 as usual. If the RP does support TAK objects it will conclude that 485 key 'A' is the one and only current key, and will proceed to validate 486 the remaining RPKI tree as usual. 488 6.2. Pre-stage a New Key 490 6.2.1. Trust Anchor 492 Now the TA prestages a new key 'B' and produces equivalent CA 493 certificates for children 'C1' and 'C2', i.e. the resources, subject 494 name, public key and SIA etc are all equivalent, but these 495 certificates are signed under key 'B'. (See Section 4 for a more 496 thorough description of this). The TAK object for key 'B' recognises 497 both keys 'A' and 'B' as current. 499 The repostory structure and TAK object for key B are then as follows: 501 +--------------------+ 502 | B.MFT | 503 +--------------------+ 504 | B.CRL | 505 | B.TAK | 506 | C1-B.CER | 507 | C2-B.CER | 508 +--------------------+ 510 +--------------------+ 511 | B.CRL | 512 +--------------------+ 513 | revocations.. | 514 +--------------------+ 516 +--------------------+ 517 | B.TAK | 518 +--------------------+ 519 | current: A, B | 520 | revoked: none | 521 +--------------------+ 523 +--------------------+ 524 | C1-B.CER | 525 +--------------------+ 526 | resources: C1 res | 527 | subject: C1 name | 528 | pub key: C1 key | 529 | SIA: C1 SIAs | 530 | AKI: B | 531 +--------------------+ 533 +--------------------+ 534 | C2-B.CER | 535 +--------------------+ 536 | resources: C2 res | 537 | subject: C2 name | 538 | pub key: C2 key | 539 | SIA: C2 SIAs | 540 | AKI: B | 541 +--------------------+ 543 When the TA is certain that the content for key 'B' is correct, it 544 can also update the TAK object for key 'A' to include 'B': 546 +--------------------+ 547 | A.TAK | 548 +--------------------+ 549 | current: A, B | 550 | revoked: none | 551 +--------------------+ 553 One way to do this is by generating a TAL 554 [I-D.ietf-sidrops-https-tal] for key B and verifying that validation 555 using this yields the same results as validation using the TAL for 556 key A would. However, note, that it is preferred that this is done 557 as part of an automated process that is sufficiently well tested, and 558 that the contents of the repositories for keys 'A' and 'B' are 559 updated as a single delta if the publication protocol [RFC8181] is 560 used (see also: Section 5). 562 6.2.2. Relying Parties 564 Relying Parties who have a TAL for key 'A' configured will discover 565 the TAK object. If the RP does not support this object, it will 566 reject this object but continue to validate the remaining RPKI tree 567 as usual. If the RP does support TAK objects it will conclude that 568 there are now two keys 'A' and 'B', and no revoked keys that it 569 should be aware of. Since key 'A' is still current, the RP will 570 continue to validate the RPKI tree structure using the repository for 571 key 'A', ignoring the non-TAK objects in the repository for key 'B'. 573 The result will be the same for Relying Parties who have a TAL for 574 key 'B' configured, because both keys are equivalent at this time. 576 6.3. Planned Key Revocation 578 6.3.1. Trust Anchor 580 The TA has now decided that key 'A' must be revoked. It still has 581 access to this key and the repository, so it can perform a planned 582 key roll. In addition to revoking key 'A', the TA will also generate 583 new key 'C' to ensure that it has at least two current keys at all 584 times for redundancy. 586 Keys 'B' and 'C' will become current keys on the TAK objects for all 587 keys: 'A', 'B' and 'C'. Key 'A' will become part of the revoked keys 588 on the TAK objects for keys 'A' and 'B'. Note that it is not needed 589 to list key 'A' as revoked on the TAK file for key 'C', because RPs 590 will only learn about key 'C' at the same time as learning about the 591 revocation of key 'A' (see also below). 593 The TA will publish a long-lived TAK file and MFT and CRL only for 594 key 'A' and publish these objects as waypointers for RPs that have a 595 TAL pointing at key 'A' before destroying key 'A'. 597 The resulting structure for key 'A' will be as follows: 599 +--------------------+ 600 | A.MFT | 601 +--------------------+ 602 | A.CRL | 603 | A.TAK | 604 +--------------------+ 606 +--------------------+ 607 | A.CRL | 608 +--------------------+ 609 | revocations.. | 610 +--------------------+ 612 +--------------------+ 613 | A.TAK | 614 +--------------------+ 615 | current: B, C | 616 | revoked: A | 617 +--------------------+ 619 The resulting structures for keys 'B' and 'C' will be as follows: 621 +--------------------+ +--------------------+ 622 | B.MFT | | C.MFT | 623 +--------------------+ +--------------------+ 624 | B.CRL | | B.CRL | 625 | B.TAK | | B.TAK | 626 | C1-B.CER | | C1-C.CER | 627 | C2-B.CER | | C2-C.CER | 628 +--------------------+ +--------------------+ 630 +--------------------+ +--------------------+ 631 | B.CRL | | C.CRL | 632 +--------------------+ +--------------------+ 633 | revocations.. | | revocations.. | 634 +--------------------+ +--------------------+ 636 +--------------------+ +--------------------+ 637 | B.TAK | | C.TAK | 638 +--------------------+ +--------------------+ 639 | current: B, C | | current: B, C | 640 | revoked: A | | revoked: | 641 +--------------------+ +--------------------+ 643 +--------------------+ +--------------------+ 644 | C1-B.CER | | C1-C.CER | 645 +--------------------+ +--------------------+ 646 | resources: C1 res | | resources: C1 res | 647 | subject: C1 name | | subject: C1 name | 648 | pub key: C1 key | | pub key: C1 key | 649 | SIA: C1 SIAs | | SIA: C1 SIAs | 650 | AKI: B | | AKI: C | 651 +--------------------+ +--------------------+ 653 +--------------------+ +--------------------+ 654 | C2-B.CER | | C2-B.CER | 655 +--------------------+ +--------------------+ 656 | resources: C2 res | | resources: C2 res | 657 | subject: C2 name | | subject: C2 name | 658 | pub key: C2 key | | pub key: C2 key | 659 | SIA: C2 SIAs | | SIA: C2 SIAs | 660 | AKI: B | | AKI: B | 661 +--------------------+ +--------------------+ 663 In addition to this the TA SHOULD reach out to RP vendors so that 664 they can update the TAL included in the RP software distribution to 665 use key 'B'. 667 6.3.2. Relying Parties 669 Relying Parties who have a TAL for key 'A' configured will discover 670 the TAK object. If the RP does not support this object, it will 671 reject this object but continue to validate the remaining RPKI tree 672 as usual. In this case that means that validation will stop, because 673 there are no more objects under key 'A'. Therefore it is important 674 that RPs that do not support TAK files are updated to use the TAL for 675 key 'B' through some other process. 677 If the RP uses a TAL for key 'A' and it supports TAK objects, it will 678 discover that the TAL for key 'A' has keys 'B' and 'C' as current, 679 and revokes itself. It will then proceed to process keys 'B' and 'C' 680 and find TALs which list the same current keys. So, it will now 681 replace its notion of the current key set for this TA based on its 682 TAL (key 'A') with what it learned. To keep things simple the RP 683 will now conclude that it should re-start validation using a 684 remaining current key, in this case key either 'B' or 'C' may be 685 used. 687 If the RP already had a TAL for key 'B' and it supports TAK objects, 688 or it simply started with key 'B' because it added it to its set of 689 current keys when this key was pre-staged (see Section 6.2), it will 690 learn that key 'A' is revoked and therefore will not attempt to 691 verify the TAK file for key 'A'. It will also learn about key 'C' 692 and inspect this key's TAL, and discover that only keys 'B' and 'C' 693 are considered current. Since it started the validation process with 694 a key that is still current, it can proceed to validate the RPKI tree 695 using the repository under key 'B'. 697 6.4. Unplanned revocation 699 6.4.1. Trust Anchor 701 Now keys 'B' and 'C' are current. The TA may have intended to revoke 702 key 'B', essentially rolling over to key 'C' and a new key 'D', but 703 let us suppose that the TA lost access to key 'C'. In this case the 704 TA will simply revoke key 'C' instead, and still introduce a new key 705 'D'. 707 The major difference with the process described above for planned 708 rolls, is that now the TA will not be able to update the TAK object, 709 MFT or CRL for key 'C'. However, because all TAL objects for current 710 keys are evaluated before tree validation is performed, it is safe to 711 leave these objects in a repository. Keys 'B' and 'D' will simply 712 mark key 'C' as being revoked. 714 If an RP still has a TAL pointing at key 'C' it will discover that 715 key 'D' is added, and that key 'B' has been revoked through the TAK 716 object published for keys 'B' and 'D'. At least, as long as the the 717 MFT and TAK EE certificates have not expired, and the CRL and MFT are 718 not stale. 720 If the TA is absolutely sure that the TAL for key 'C' never shipped 721 with any RP distribution, then it would also be safe to delete the 722 repository key 'C' altogether. RPs will learn that 'C' is revoked, 723 and therefore will not even attempt to download the TAK object. 724 However, it is hard to be certain of this and there this is NOT 725 RECOMMENDED. 727 7. Deployment Considerations 729 Including Signed TAL objects while RP tools do not support this 730 standard will result in these RPs rejecting these objects. It is not 731 expected that this will result in the invalidation of any other 732 object under a Trust Anchor. 734 That said, the flagging mechanism introduced here can only be relied 735 on once a majority of RPs support it. Defining when that moment 736 arrives is by definition something that cannot be established at the 737 time of writing this document. Until such time, TAs SHOULD continue 738 to generate unsigned TAL files [I-D.ietf-sidrops-https-tal], and 739 indicate which should be considered their current TAL, and 740 communicate them to RPs through other means. 742 However, once a majority of RPs support this mechanism it would be 743 RECOMMENDED that Trust Anchor operators perform key rolls regularly. 744 The most assured way to know that such key rolls will work is by 745 making them a part of normal operations. Determining when this 746 moment arrives is by definition out of scope for this document, as it 747 should be based on operational experience. 749 8. IANA Considerations 751 8.1. OID 753 IANA is to add the following to the "RPKI Signed Objects" registry: 755 Decimal | Description | References 756 --------+--------------------------------+--------------- 757 TBD | Trust Anchor Keys | [section 3.1] 759 8.2. File Extension 761 IANA is to add an item for the Signed TAL file extension to the "RPKI 762 Repository Name Scheme" created by [RFC6481] as follows: 764 Extension | RPKI Object | References 765 -----------+------------------------------------------- 766 .tak | Trust Anchor Keys | [this document] 768 9. Security Considerations 770 TBD 772 10. Acknowledgements 774 The authors wish to thank Martin Hoffmann for a thourough review of 775 this document. 777 11. References 779 11.1. Normative References 781 [I-D.ietf-sidrops-https-tal] 782 Huston, G., Weiler, S., Michaelson, G., Kent, S., and T. 783 Bruijnzeels, "Resource Public Key Infrastructure (RPKI) 784 Trust Anchor Locator", draft-ietf-sidrops-https-tal-05 785 (work in progress), October 2018. 787 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 788 Requirement Levels", BCP 14, RFC 2119, 789 DOI 10.17487/RFC2119, March 1997, 790 . 792 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 793 Addresses and AS Identifiers", RFC 3779, 794 DOI 10.17487/RFC3779, June 2004, 795 . 797 [RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI 798 Scheme", RFC 5781, DOI 10.17487/RFC5781, February 2010, 799 . 801 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for 802 Resource Certificate Repository Structure", RFC 6481, 803 DOI 10.17487/RFC6481, February 2012, 804 . 806 [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route 807 Origin Authorizations (ROAs)", RFC 6482, 808 DOI 10.17487/RFC6482, February 2012, 809 . 811 [RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski, 812 "Manifests for the Resource Public Key Infrastructure 813 (RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012, 814 . 816 [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for 817 X.509 PKIX Resource Certificates", RFC 6487, 818 DOI 10.17487/RFC6487, February 2012, 819 . 821 [RFC6488] Lepinski, M., Chi, A., and S. Kent, "Signed Object 822 Template for the Resource Public Key Infrastructure 823 (RPKI)", RFC 6488, DOI 10.17487/RFC6488, February 2012, 824 . 826 [RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification 827 Authority (CA) Key Rollover in the Resource Public Key 828 Infrastructure (RPKI)", BCP 174, RFC 6489, 829 DOI 10.17487/RFC6489, February 2012, 830 . 832 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 833 Protocol (HTTP/1.1): Message Syntax and Routing", 834 RFC 7230, DOI 10.17487/RFC7230, June 2014, 835 . 837 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 838 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 839 May 2017, . 841 [RFC8181] Weiler, S., Sonalker, A., and R. Austein, "A Publication 842 Protocol for the Resource Public Key Infrastructure 843 (RPKI)", RFC 8181, DOI 10.17487/RFC8181, July 2017, 844 . 846 [X.690] ITU-T Recommendation X.690 (2002) | ISO/IEC 8825-1:2002, 847 "Information technology - ASN.1 encoding rules: 848 Specification of Basic Encoding Rules (BER), Canonical 849 Encoding Rules (CER) and Distinguished Encoding Rules 850 (DER)", 2002. 852 11.2. Informative References 854 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 855 RFC 5652, DOI 10.17487/RFC5652, September 2009, 856 . 858 Authors' Addresses 860 Tim Bruijnzeels 861 NLnet Labs 863 Email: tim@nlnetlabs.nl 864 URI: https://www.nlnetlabs.nl/ 866 Carlos Martinez 867 LACNIC 869 Email: carlos@lacnic.net 870 URI: https://www.lacnic.net/ 872 Rob Austein 873 Dragon Research Labs 875 Email: sra@hactrn.net